Abstract: A disclosure of the present specification provides a method for transferring downlink data by a serving gateway (S-GW). The method may comprise the steps of: transmitting a downlink data notification (DDN) message to a mobility management entity (MME) and a serving general packet radio service (GPRS) supporting node (SGSN), when downlink data arrives at a wireless device in a state where an idle mode signaling reduction (ISR) is activated; receiving a message notifying of a DDN refusal from any one of the MME and SGSN when the wireless device, being in a power saving mode (PSM), cannot receive the downlink data; and transmitting a paging stop request message to any one of the MME and SGSN when the message indicating the refusal of the DDN is received.